Distraction instrument with fins for maintaining insertion location

ABSTRACT

A tip for a medical device that distracts two opposing vertebral bodies. The tip has a hub, a boss, and a first longitudinal fin. The boss is attached the hub and has a body, a tapered portion, and a vertex. The first fin is attached to the boss, and projects from at least a portion of the boss&#39;s external surface. The first fin then extends over at least a portion of the length of the body and substantially extends over the length of the tapered portion.

REFERENCE TO RELATED APPLICATIONS

This is a continuation application of co-pending U.S. patent applicationSer. No. 09/418,741 filed Oct. 15, 1999, now U.S. Pat. No. 6,277,122owned by the assignee of the present application.

The present invention relates to an apparatus for separating vertebralbodies to perform surgery or install implants in the disc space betweenvertebral bodies, and more specifically relates to an apparatus with oneor more fins that extend from a substantial part of the tapered end andthe body of the apparatus in order to maintain its insertion locationbetween the vertebrae.

BACKGROUND

Distraction is a common surgical procedure to operate on the spine. Itis used to prepare a spine for fusing two opposing (adjacent) vertebraeor to install an implant in the disc space between two opposingvertebrae. Distraction can be performed anteriorly (from the front ofthe patient) or posteriorly (from the back). But regardless of theapproach, the procedure generally begins by first exposing that portionof the spine, which the surgeon has determined to require repair, andthen removing all or part of the damaged spinal disc between the twoopposing vertebrae in question.

After removing the spinal disc, the surgeon then typically inserts whatthe layperson may describe as one or more wedges between the twovertebrae. Each wedge is mounted on the end of a shaft and successivelytaller wedges are inserted between the two vertebrae until the surgeonobtains the desired separation (“distraction”) between them. Once thedesired separation is obtained, the surgeon then slides what thelayperson may describe as a special tube over the shaft while the lastwedge is still located between the vertebrae. This special tube is oftenreferred to as a “guide sleeve”. The guide sleeve is generally tallerthan the wedge that separates the vertebrae. Hence, the distal end (theend toward the patient) of the guide sleeve butts against the outside ofthe top and bottom vertebrae. Typically, the guide sleeve has a topspike and bottom spike that extend from its distal end, and these spikesare respectively placed in contact with the top and bottom vertebrae.Further, the end of the guide sleeve may have lateral extensions toextend into the disc space between the top and bottom vertebrae andaround each side of the wedge. The spikes are then driven into thevertebrae by striking the proximal end of the outside sleeve distractorwith a hammer or some other impact device. With the spikes placed intothe vertebrae and the lateral extensions slid in the disc space, thewedge is no longer necessary to hold the vertebrae apart. The spikes andlateral extensions now serve that function, and the wedge can be pulledout from the disc space through the inside of the guide sleeve. With thewedge removed, the surgeon is then free to work through the inside ofthis special tube to prepare the disc space for fusion or installimplants.

With the foregoing explanation in mind, some nomenclature is importantto fully understand the following specification. If the wedge/tip usedto separate the vertebrae is approximately as tall as it is wide, theoperation is called a “single barrel” procedure. Alternatively, if thewedge/tip is approximately twice as Side as it is tall, the operation iscalled a “double barrel” procedure. This terminology has largely risenfor metaphoric reasons. The cross-section of a guide sleeve used in adouble-barrel procedure resembles the cross-section of a double-barrelshotgun, and the cross-section of the guide sleeve used in asingle-barrel procedure resembles the cross-section of a single-barrelshotgun.

The insertion location of the wedges between the vertebrae is ofcritical importance in most any surgery involving vertebral distraction.The wedge/tip determines the placement of the guide sleeve, which inturn commonly determines the exact placement of an implant or fusionmaterial within the disc space. Hence, prior art devices, such as thatpresented in U.S. Pat. No. 5,484,437 to Michelson seek to limitinadvertent migration of the wedge by incorporating sharp pegs into thetop and bottom sides of the wedge. The pegs in that design, however, donot contact vertebral tissue until the distractor/wedge has all butfully separated the vertebrae in question. As a result, that prior artdesign may allow the distractor/wedge to migrate during insertion intothe vertebral space, before the sharp pegs have the opportunity tofunction.

What is needed is a medical device that can immediately secure itsposition within the disc space between two vertebral bodies, once thesurgeon places the device in contact with the spine. The followingdevices address this need.

SUMMARY OF THE INVENTION

In one aspect, this invention is a tip for a medical device thatdistracts two opposing vertebral bodies. The tip has (1) a hub, (2) aboss, and (3) a first longitudinal fin. The boss is attached to the huband has a body, a tapered portion, and a vertex. The first longitudinalfin is attached to the boss, and projects from at least a portion of theboss's external surface. But in addition, the first longitudinal finalso extends over at least a portion of the length of the body andsubstantially extends over the length of the tapered portion of theboss.

In another aspect, this invention is a tip for a medical device thatdistracts two opposing vertebral bodies. The tip has (1) a hub, (2) aboss, (3) a first longitudinal fin, and (4) a second longitudinal fin.The boss is attached to the hub and has a body, a tapered portion, and avertex. The first and second longitudinal fins are attached to the boss,and project from at least a portion of the boss's external surface. Butin addition, the longitudinal fins also extend over at least a portionof the length of the body and substantially extend over the length ofthe tapered portion of the boss.

As used in this specification, the term “hub” is a part of thisinvention that holds the boss. The hub may have various shapes such as awedge, a tube, a rectangle, a square, a parabola, or a dome.

As used in this specification, the term “boss” is a part of thisinvention that holds the longitudinal fins. The boss may have variousshapes such as a wedge, a tube, a rectangle, a square, a parabola, or adome.

As used in this specification, the term “substantially extending overthe length of said tapered portion”, which is used to describe theplacement of a longitudinal fin on the present invention, means that thelongitudinal fin distally extends over the tapered portion for no lessthan about 40 percent of the total length of the tapered portion,measured over the external surface of the tapered portion, between thetapered portion's proximal and distal ends.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tip for a medical device to distracttwo opposing vertebral bodies according to one embodiment of the presentinvention.

FIG. 2 is a plan view of a tip for a medical device to distract twoopposing vertebral bodies according to one embodiment of the presentinvention.

FIG. 3 is a side elevation view of a tip for a medical device todistract two opposing vertebral bodies according to one embodiment ofthe present invention.

FIG. 4 is a side elevation view of a longitudinal fin, which may be usedto practice the present invention.

FIG. 5 is a side elevation view of a medical device to distract twoopposing vertebral bodies according to another embodiment of the presentinvention.

FIG. 6 is a plan view of a medical device to distract two opposingvertebral bodies according to another embodiment of the presentinvention.

FIGS. 7-10 are respectively a perspective view, a plan view, an endview, and a cross-sectional view of a boss, which may be used topractice the present invention.

FIGS. 11-12 are respectively a side elevation view and an end view of ashaft, which may used to practice the present invention.

FIGS. 13-15 are respectively a perspective view, a plan view, and an endview of an aft guide, which may be used to practice the presentinvention.

FIGS. 16 and 17 are respectively a front perspective view and a rearperspective of a hub, which may be used to practice the presentinvention.

FIGS. 18-20 are respectively a plan view, side cross-section view, andan end view of a hub, which may be used to practice the presentinvention.

FIG. 21 is a side elevation view of one embodiment of the presentinvention being inserted between two opposing vertebral bodies.

FIGS. 22-24 are respectively a top, side, and bottom view of yet anotherembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, and that such alterations and furthermodifications in the illustrated device and that such furtherapplications of the principles of the invention as illustrated thereinare contemplated as would normally occur to one skilled in the art towhich the invention pertains.

Referring now to FIGS. 1-3, there is shown a tip 30 for a medical devicethat distracts two opposing vertebral bodies according to one embodimentof the present invention. Tip 30 includes a hub 31, a boss 34, and alongitudinal fin 35. Hub 31 has a proximal end 32, a distal end 33, andmeans for connecting proximal end 32 to the distal end of a medicaldevice (not shown). In this embodiment, the means for connectingproximal end 32 to a medical device are female screw threads 36. As iscommon in the art, these threads are created by first drilling hole 44into hub 31, followed by tapping threads 36 into the walls of hole 44.However besides female screw threads, other connecting means arecontemplated to practice the present invention such as male screwthreads, pinning, or welding. The end of hub 31 is also shown with bands56 and 40. These bands are preferably colored to designate a tip of aparticular size.

Boss 34 has a proximal end 37, a distal end 38, and a body 50 locatedbetween ends 37 and 38. Proximal end 37 is fixedly secured to the distalend 33 of hub 31 in any appropriate manner such as welding, however,both hub 31 and boss 34 are more preferably manufactured by directlymachining hub 31 and boss 34 from a common piece of material.Nevertheless, hub 31 is also preferably larger than boss 34 so as toform shoulder 55 between hub 31 and boss 34. Body 50 has a length 60(FIG. 3), and preferably, length 60 is such that tip 30 will not overlypenetrate the disc space when shoulder 55 butts against the outside ofthe vertebrae. The distal end 38 of boss 34 is closed and preferablygets thinner at tapered portion 62 over a surface length 61 to a vertex39. Similar to hub 31, boss 34 is cut with bands 41, 42, and 43;however, unlike the bands in the hub, these bands in boss 34 serve toengage tissue when the tip is in use. Finally, boss 34 is also cut withslot 45 to hold longitudinal fin 35, and preferably, slot 45 is cutcompletely through boss 34.

Now referring to FIGS. 1-4, longitudinal fin 35 has a proximal end 46and a distal end 47 that preferably extends from boss 34 at vertex 39and continues to extend from boss 34 for the entire surface length 61 oftapered portion 62. However, it is also contemplated that longitudinalfin 35 does not extend from surface length 61 for its entire dimension,that is from its distal end at vertex 39 to its proximal end 59. In thisregard, it is also contemplated that longitudinal fin 35 may also becoterminous with the tapered portion (or simply does not extend from thesurface of the tapered portion at this location) for up to about the 60percent of surface length 61. And more preferably does not so extend forup to about the first, distal 60 percent of surface length 61. In otherwords, the fin 35 will extend from tapered portion 62 for about 40percent or more of length 61 and leave a remaining 60 percent or lesswithout a fin. But again, more preferably longitudinal fin 35 willextend from tapered portion 62 for about the first, proximal 40 percentor more of length 61 and leave a remaining distal 60 percent or lesswithout a fin. An example of a 60 percent coterminous profile isdepicted by the dashed line 64 in FIG. 4 with the dashed linerepresenting the outside limits of boss 34 that reside next to fin 35.Dashed lines 65 and 66 respectively represent a fin with about a 20percent and about a 10 percent coterminous profile.

Longitudinal fin 35 is preferably mechanically held in slot 45 by pins54 (FIG. 3) or by a weld (not shown). The proximal end 46 oflongitudinal fin 35 is preferably straight to ride against the bottom 48of slot 45. The distal end 47, however, preferably terminates at asecond vertex 49. Then as shown, longitudinal fin 35 preferablycontinues from vertex 49 to project laterally around the tapered portion62 of distal end 38 and down at least a portion of body 50. Moreover,although longitudinal fin 35 is shown in FIG. 3 wrapping around both thetop side 52 and the bottom side 53 of boss 34, it is also contemplatedthat longitudinal fin 35 may project only from one of these sides, notboth. And still further, though fin 35 is shown as a separate piece, itis further contemplated that fin 35 and boss 34 are cast or machinedfrom a common piece of material.

The tip shown in FIGS. 1-3 would typically be used in a single-barrelprocedure and is further of a design that is capable of being removablyattached to a medical device. In this regard, the reader should takenote the present invention may take other forms. For example, thissingle barrel design could be permanently secured to a shaft as part ofa larger medical device that is used to distract two opposing vertebrae,or this tip could be widened for use in a double-barrel procedure. Forthe convenience of the reader, an embodiment incorporating both of theseoptions follows.

Referring now to FIGS. 5 and 6, there is shown a medical device 80 thatdistracts two opposing vertebral bodies according to another embodimentof the present invention. Medical device 80 includes a shaft 81, a hub82, a boss 92, a first longitudinal fin 83, and a second longitudinalfin 84. Hub 82 has a proximal end 85, a distal end 86, and means forconnecting proximal end 85 of hub 82 to the distal end 87 of shaft 81.In this embodiment, the means for connecting proximal end 85 to shaft 81is a pin and a weld. As is common in the art, such a joint is created byfirst drilling a hole 88 into hub 82 that is of slightly larger diameterthan shaft 81. Shaft 81 is then inserted into hole 88, which is followedby drilling a much smaller hole 89 into the side of hub 82 and shaft 81then inserting a pin 90 of appropriate diameter into hole 89. Thecircumference of shaft 81 is then welded to bole 88 at 91, and pin 90 isfinished flush with the external surface of hub 82. However, besidespinning and welding, other connecting means are contemplated to practicethe present invention such as mating male and female screw threads.Further details of Hub 82 using the same reference numerals as in FIGS.5 and 6 are shown in FIGS. 16-20.

Referring now to FIGS. 5-10, boss 92 has a proximal end 93, a distal end94, and a body 95 located between ends 93 and 94. Proximal end 93 isfixedly secured to the distal end 86 of hub 82 in any appropriatemanner, such as being cast as a single piece, or machined from a singlepiece of material; however, boss 92 and hub 82 are preferably firstpinned, then welded together. In this regard, proximal end 93 is placedin a mating slot 96 in hub 82 (FIGS. 16, 19, 20). Holes 97 (FIGS. 5, 6)are then drilled through hub 82 and boss 92, which is then followed bypinning (98) and welding the pins into place. Here again, as in thepreviously presented embodiment, hub 82 is preferably slightly largerthan boss 92 so as to from shoulder 100 between hub 82 and boss 92. Body95 has a length 170 (FIG. 10), and preferably length 170 is such thatdevice 80 will not overly penetrate the disc space when shoulder 100butts against the outside of the vertebrae. The distal end 94 of boss 92is closed and preferably gets thinner at tapered portion 171 over asurface length 172 to a vertex 101. Similar to the grooves cut in theboss of the previous embodiment, boss 92 is cut, preferably on eachside, with grooves 102, 103, and 104 (FIGS. 7 and 8), which serve toengage tissue when the medical device is in use. Finally boss 92 is alsocut with slots 105 and 106, and channels 107 (FIGS. 7-9). Slots 105 and106 are preferably cut completely through boss 92. These slots are usedto hold a first longitudinal fin 83 and a second longitudinal fin 84.Channels 107 serve to inform the user where the midline of medicaldevice 80 is located when the device is in use and placed between twovertebrae.

Now referring to FIGS. 4-6, longitudinal fins 83 and 84 are preferablyidentical to previously presented longitudinal fin 35, however, for theconvenience of the reader, this information will be presented againusing different reference numerals for this embodiment of the presentinvention. Longitudinal fins 83 and 84 have a distal end 108 and aproximal end 109 that preferably extends from boss 92 at vertex 101 andcontinues to extend from boss 92 for the entire surface length 172 oftapered portion 171. However, it is also contemplated that longitudinalfins 83 and 84 do not extend from surface length 171 for its entiredimension. That is from tapered portion's distal end at vertex 101 toits proximal end 199 (or simply does not extend from the surface of thetapered portion at this location) for up to about 60 percent of surfacelength 172. And preferably does not extend for up to about the first,distal 60 percent of surface length 172. In other words, longitudinalfins 83 and 84 will extend from tapered portion 171 for about 40 percentor more of length 172 and leave a remaining 60 percent or less without afin. But again, preferably longitudinal fins 83 and 84 will extend fromtapered portion 171 for about the first, proximal 40 percent or more oflength 172 and leave a remaining distal 60 percent or less without afin. Examples of 60 percent, 20 percent, and 10 percent coterminousprofiles are shown in previously presented FIG. 4 at dashed lines 64,65, and 66.

Longitudinal fins 83 and 84 are preferably mechanically held in slots105 and 106 by pins 110 or a weld (not shown). The proximal ends 109 oflongitudinal fins 83 and 84 are preferably straight to ride against thebottom 111 (FIG. 8) of slots 105 and 106. The distal end 108, however,preferably terminates at a second vertex 112. Longitudinal fins 83 and84 each then preferably continue from vertex 112 to project laterallyaround distal end 94 of boss 92 and down at least a portion of body 95.Moreover, although longitudinal fins 83 and 84 are shown in FIG. 5wrapping around both the top side 115 and the bottom side 116 of boss92, it is also contemplated that longitudinal fins 83 and 84 eachproject only from one of these sides, not both.

Referring now to FIGS. 5, 6, and 13-15, medical device 80 preferablyalso includes aft guide 140 fixedly secured to shaft 81. Both aft guide140 and hub 82 preferably have a cross-section to slide within an outerdistractor sleeve. And here, the distractor would be one typically usedin a double-barrel procedure because, referring to FIG. 15, thecross-section of aft guide 140 is approximately twice as wide as it istall and resembles a figure “8”. In this embodiment, aft guide 140 isfirst drilled at 144 to a diameter that is slightly larger than shaft81. Thereafter, aft guide 140 is slid over shaft 81 and located over thelength of shaft 81 at a desired location in line with hub 82 and boss92. Aft guide 140 is then first pinned at 141 and then welded at 142 and143 to secure it to shaft 81. Beyond pinning and welding, other methodsto attach aft guide 140 to shaft 81 are contemplated by this invention,for example, by casting aft guide 140 and shaft 81 from a common pieceof material.

Additional details of shaft 81 are further shown in FIGS. 11 and 12. Thearea 150, which is proximal to aft guide 140, is preferably knurled at151 to assist the user in gripping the device. Moreover, the proximalend 152 of shaft 81 is further adapted at 153 to accept a removablehandle (not shown). In this embodiment, the adaptation 153 comprises amale fitting with two flat sides 154 and 155. A complementary femalefitting, which is attached to a handle, then engages shaft 81 by slidingover the male fitting. The handle can then control rotation of the shaftbecause the mating female fitting has complementary flat sides (notshown) that ride against mating flat sides 104, 105 on end of shaft 81.

Each of the foregoing embodiments of the present invention is generallyused in the same manner. With the spinal disc removed, the surgeonplaces the leading edge of the longitudinal fins on the distal end ofthe distractor device into the disc space and against the surroundingvertebrae 200, 201. (FIG. 21) Once properly located, the surgeon thendrives the distal end of the distractor device between the vertebrae andinto the disc space 202. Upon entry, the longitudinal fins immediatelycut into the surrounding vertebrae, which helps prevent the distractordevice from deviating from the desired line of entry. A surgeontypically drives the device into the disc space until shoulder 55 or 100comes to rest against the outside of vertebrae 200, 201. Once fullyinserted, the surgeon typically either removes the device and reinsertsa taller device to further separate the vertebrae, or if the desiredseparation has been reached, the surgeon installs a guide sleeve. Withthe guide sleeve in place, the surgeon then removes the device frombetween the vertebrae and continues the rest of the operation throughthe guide sleeve.

Referring now to FIGS. 22-24, there is shown yet another embodiment ofthe present invention. For the convenience of the reader, like numeralshave been used to identify similar parts of this invention as that usedin the embodiment shown in FIGS. 5-10. The embodiment shown in FIGS.22-24, however, is for use when the surgeon must approach the spine froman angle. Here, medical distractor 80 has an oblique edge 300, which istypically required for the surgeon to distract adjacent vertebral bodiesfrom a non-perpendicular angle. Relevant here, oblique angle 300emphasizes the importance of the present invention. Longitudinal fin 83helps insure that medical distractor 80 will maintain the proper line ofinsertion, even though oblique angle 300 may tend to force distractor 80to move laterally. Immediately upon contact with the vertebral bodies,longitudinal fin 83 cuts into the vertebrae to help maintain the properline of insertion into the disc space even before oblique angle 300 hasthe opportunity to cause a lateral misalignment.

An advantage of this invention over the prior art largely rests in theunique placement of the longitudinal fins 35 or 83-84 over a substantialpart of the tapered portion of the boss that supports the longitudinalfin. Unlike the devices found in the prior art, the present inventionplaces one or more guiding longitudinal fins in contact with vertebralbodies before they are fully distracted. This placement allows thelongitudinal fins to help maintain the surgeon's line of insertionbefore the distractor device starts to separate the opposing vertebrae.And this assistance is far from minor. As explained earlier, thelocation of these “wedges” within the disc space can ultimatelydetermine the exact placement of spinal implants or fusion material.Hence, maintaining the proper line of insertion of a distractor deviceat the start is important to help assure that the surgery willultimately be a success.

What is claimed is:
 1. A distraction member for distracting a disc spacebetween adjacent vertebral bodies, comprising: a distraction tip adaptedfor insertion between the adjacent vertebral bodies to distract the discspace; and at least one fin secured to said distraction tip, at least aportion of the at least one fin extending transversely from saiddistraction tip and adapted to engage a corresponding one of theadjacent vertebral bodies.
 2. The distraction member of claim 1, whereinportions of the at least one fin extend transversely from opposite sidesof said distraction tip.
 3. The distraction member of claim 1, whereinsaid at least one fin extends beyond a distal end of said distractiontip.
 4. A distraction member for distracting a disc space betweenadjacent vertebral bodies, comprising: a distraction tip adapted forinsertion between the adjacent vertebral bodies to distract the discspace, said distraction tip having a tapered distal portion; and atleast one fin, at least a portion of the fin extending transversely fromsaid distraction tip and adapted to engage a corresponding one of theadjacent vertebral bodies.
 5. The distraction member of claim 4, saidtapered distal portion of said distraction tip defines a vertex.
 6. Thedistraction member of claim 5, wherein said at least one fin iscoterminous with said vertex.
 7. The distraction member of claim 5,wherein a portion of said at least one fin projects distally beyond saidvertex.
 8. The distraction member of claim 4, wherein said at least onefin extends beyond a distal end of said distraction tip.
 9. Adistraction member for distracting a disc space between adjacentvertebral bodies, comprising: a distraction tip adapted for insertionbetween the adjacent vertebral bodies to distract the disc space; a hubextending axially from said distraction tip, a portion of said hubextending transversely beyond said distraction tip to form a shoulder;and at least one fin, at least a portion of the fin extendingtransversely from said distraction tip and adapted to engage acorresponding one of the adjacent vertebral bodies.
 10. The distractionmember of claim 9, wherein said at least one fin extends beyond a distalend of said distraction tip.
 11. A method for establishing a disc spaceheight between two adjacent vertebral bodies, comprising: providing adistraction member having a distraction tip and at least onelongitudinally extending fin secured to said tip; positioning the tipagainst the adjacent vertebral bodies; and advancing the distraction tipbetween the adjacent vertebral bodies to restore the disc space height,the fin in intimate engagement with at least one of the adjacentvertebral bodies.
 12. The method of claim 11, wherein the tip includes adistal end and the fin extends beyond the distal end, and thepositioning includes inserting the distal end of the fin into the discspace prior to the distraction tip entering the disc space.
 13. Themethod of claim 11, wherein the distraction tip includes an atramaticleading tip and the fin extends above the surface of the atramatic tipsuch that upon advancement into the disc space, the fin engages at leastone of the upper and lower vertebral bodies prior to engagement with theatramatic insertion tip.
 14. The method of claim 11, further includingproviding a second distraction member having a fin; positioning thesecond distraction member with a fin adjacent the disc space laterallyspaced from and in substantial alignment with the first distractionmember; and advancing the first and second distraction members into thedisc space.
 15. A method for distracting a disc space between twoadjacent vertebral bodies, comprising: providing a distraction memberhaving a distraction tip sized for insertion within the disc space andat least one longitudinally extending fin secured to the distractiontip; inserting the distraction tip between the adjacent vertebralbodies; and engaging the fin with a corresponding one of the adjacentvertebral bodies.
 16. The method of claim 15, wherein the fin extendsbeyond a distal end of the distraction tip; and further comprisingpositioning the distal end of the fin into the disc space prior to theinserting.
 17. The method of claim 15, wherein at least a portion of thefin extends transversely from the distraction tip, and wherein theengaging occurs prior to the inserting.
 18. The method of claim 15,wherein the engaging comprises cutting into the at least one of theadjacent vertebral bodies.
 19. The method of claim 15, wherein theengaging maintains an orientation of the distraction tip during theinserting.
 20. The method of claim 15, wherein the distraction memberincludes an atramatic tip and the fin extends above a surface of theatramatic tip such that upon advancement into the disc space, the finengages at least one of the adjacent vertebral bodies prior toengagement with the atramatic tip.